The billable area is a sum of interior areas of all floors (including below grade), plus all spaces that may be excluded from the interior floor area totals for the purpose of property size reporting standards, such as sunrooms, crawlspaces, any rooms attached to the house that can only be accessed from outside and parts of rooms with sloped ceilings where the height of the room is less than 5 ft. Exterior wall thickness does not affect the billable area as it only affects the exterior floor area.

No charge for attached garages (main building only) and outdoor spaces such as balconies, decks and patios. Garages that are part of additional buildings are billable.